A web server should be primarily a web server or a proxy server but not both, for the same reasons that other multi-use servers are not recommended. Scanning for web servers that will also proxy requests into an otherwise protected network is a very common attack making the attack anonymous.
Check
Review the web server documentation and deployed configuration to determine if the web server is also a proxy server.
If the web server is also acting as a proxy server, this is a finding.
Fix
Uninstall any proxy services, modules, and libraries that are used by the web server to act as a proxy server.
Verify all configuration changes are made to assure the web server is no longer acting as a proxy server in any manner.